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Average Weather at San Marcos Automatic Weather Observing / Reporting System Texas, United States

At San Marcos Automatic Weather Observing / Reporting System, the summers are hot and muggy; the winters are short, cold, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 40°F to 96°F and is rarely below 28°F or above 100°F.

Climate Summary

coolcomfortablewarmhothotwarmcoolJanFebMarAprMayJunJulAugSepOctNovDec72%72%54%54%clearovercastprecipitation: 3.9 inprecipitation: 3.9 in1.3 in1.3 inmuggy: 77%muggy: 77%0%0%drydrybeach/pool score: 6.6beach/pool score: 6.60.60.6
Click on each chart for more information.

Based on the beach/pool score, the best time of year to visit San Marcos Automatic Weather Observing / Reporting System for hot-weather activities is from late May to mid September.

Temperature

The hot season lasts for 3.6 months, from June 2 to September 20, with an average daily high temperature above 89°F. The hottest day of the year is August 10, with an average high of 96°F and low of 74°F.

The cool season lasts for 2.8 months, from November 27 to February 21, with an average daily high temperature below 68°F. The coldest day of the year is January 5, with an average low of 40°F and high of 61°F.

Average High and Low Temperature

Average High and Low Temperature at San Marcos Automatic Weather Observing / Reporting SystemhotcoolcoolJanFebMarAprMayJunJulAugSepOctNovDec0°F10°F20°F30°F40°F50°F60°F70°F80°F90°F100°FJan 561°FJan 561°FAug 1096°FAug 1096°F40°F40°F74°F74°FJun 289°FJun 289°FSep 2089°FSep 2089°FNov 2768°FNov 2768°FFeb 2168°FFeb 2168°F70°F70°F68°F68°F47°F47°F46°F46°FLowHigh
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature

Average Hourly Temperature at San Marcos Automatic Weather Observing / Reporting SystemJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMcoldcoldcoldcoldcoolcoolcomfortablewarmhotvery coldcomfortablevery cold
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Medenine, Tunisia (6,043 miles away) and Meipu, China (7,869 miles) are the far-away foreign places with temperatures most similar to San Marcos Automatic Weather Observing / Reporting System (view comparison).

Clouds

At San Marcos Automatic Weather Observing / Reporting System, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year at San Marcos Automatic Weather Observing / Reporting System begins around May 6 and lasts for 2.0 months, ending around July 7. On June 11, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 72% of the time, and overcast or mostly cloudy 28% of the time.

The cloudier part of the year begins around July 7 and lasts for 10.0 months, ending around May 6. On January 3, the cloudiest day of the year, the sky is overcast or mostly cloudy 46% of the time, and clear, mostly clear, or partly cloudy 54% of the time.

Cloud Cover Categories

Cloud Cover Categories at San Marcos Automatic Weather Observing / Reporting SystemclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Jun 1172%Jun 1172%Jan 354%Jan 354%May 663%May 663%Jul 763%Jul 763%clearmostly clearpartly cloudymostly cloudyovercast
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at San Marcos Automatic Weather Observing / Reporting System varies throughout the year.

The wetter season lasts 5.8 months, from April 28 to October 22, with a greater than 24% chance of a given day being a wet day. The chance of a wet day peaks at 33% on May 29.

The drier season lasts 6.2 months, from October 22 to April 28. The smallest chance of a wet day is 14% on December 16.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 33% on May 29.

Daily Chance of Precipitation

Daily Chance of Precipitation at San Marcos Automatic Weather Observing / Reporting SystemwetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%May 2933%May 2933%Dec 1614%Dec 1614%Apr 2824%Apr 2824%Oct 2224%Oct 2224%rain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. San Marcos Automatic Weather Observing / Reporting System experiences significant seasonal variation in monthly rainfall.

Rain falls throughout the year at San Marcos Automatic Weather Observing / Reporting System. The most rain falls during the 31 days centered around May 25, with an average total accumulation of 3.9 inches.

The least rain falls around August 1, with an average total accumulation of 1.3 inches.

Average Monthly Rainfall

Average Monthly Rainfall at San Marcos Automatic Weather Observing / Reporting SystemJanFebMarAprMayJunJulAugSepOctNovDec0 in2 in4 in6 in8 inMay 253.9 inMay 253.9 inAug 11.3 inAug 11.3 inOct 183.1 inOct 183.1 inMar 132.1 inMar 132.1 inJan 211.6 inJan 211.6 in
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

The length of the day at San Marcos Automatic Weather Observing / Reporting System varies significantly over the course of the year. In 2017, the shortest day is December 21, with 10 hours, 13 minutes of daylight; the longest day is June 20, with 14 hours, 4 minutes of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight at San Marcos Automatic Weather Observing / Reporting SystemJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 6 minMar 2012 hr, 6 minMar 2014 hr, 4 minJun 2014 hr, 4 minJun 2012 hr, 8 minSep 2212 hr, 8 minSep 2210 hr, 13 minDec 2110 hr, 13 minDec 21nightnightday
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 6:29 AM on June 10, and the latest sunrise is 1 hour, 18 minutes later at 7:47 AM on November 4. The earliest sunset is at 5:31 PM on December 1, and the latest sunset is 3 hours, 5 minutes later at 8:36 PM on June 30.

Daylight saving time (DST) is observed at San Marcos Automatic Weather Observing / Reporting System during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.

Sunrise & Sunset with Twilight and Daylight Saving Time

Sunrise & Sunset with Twilight and Daylight Saving Time at San Marcos Automatic Weather Observing / Reporting SystemJanFebMarAprMayJunJulAugSepOctNovDec2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 106:29 AMJun 106:29 AM8:36 PMJun 308:36 PMJun 30Dec 15:31 PMDec 15:31 PM7:47 AMNov 47:47 AMNov 4Mar 12DSTMar 12DSTDSTNov 5DSTNov 5daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2017. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

San Marcos Automatic Weather Observing / Reporting System experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 6.0 months, from April 24 to October 23, during which time the comfort level is muggy, oppressive, or miserable at least 20% of the time. The muggiest day of the year is July 3, with muggy conditions 77% of the time.

The least muggy day of the year is January 23, when muggy conditions are essentially unheard of.

Humidity Comfort Levels

Humidity Comfort Levels at San Marcos Automatic Weather Observing / Reporting SystemmuggyJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jan 230%Jan 230%77%Jul 377%Jul 3Apr 2420%Apr 2420%Oct 2320%Oct 2320%oppressiveoppressivemuggymuggyhumidhumiddrydrycomfortablecomfortablemiserablemiserable
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at San Marcos Automatic Weather Observing / Reporting System experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.4 months, from October 30 to June 13, with average wind speeds of more than 9.3 miles per hour. The windiest day of the year is April 2, with an average hourly wind speed of 10.8 miles per hour.

The calmer time of year lasts for 4.5 months, from June 13 to October 30. The calmest day of the year is September 5, with an average hourly wind speed of 7.8 miles per hour.

Average Wind Speed

Average Wind Speed at San Marcos Automatic Weather Observing / Reporting SystemwindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph2 mph4 mph6 mph8 mph10 mph12 mph14 mph16 mphApr 210.8 mphApr 210.8 mphSep 57.8 mphSep 57.8 mphOct 309.3 mphOct 309.3 mphJun 139.3 mphJun 139.3 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction at San Marcos Automatic Weather Observing / Reporting System varies throughout the year.

The wind is most often from the south for 10 months, from February 3 to December 8, with a peak percentage of 78% on July 14. The wind is most often from the north for 1.8 months, from December 8 to February 3, with a peak percentage of 41% on January 1.

Wind Direction

Wind Direction at San Marcos Automatic Weather Observing / Reporting SystemNSNJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%southnortheastwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Best Time of Year to Visit

To characterize how pleasant the weather is at San Marcos Automatic Weather Observing / Reporting System throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best times of year to visit San Marcos Automatic Weather Observing / Reporting System for general outdoor tourist activities are from early April to mid June and from mid September to late October, with a peak score in the first week of October.

Tourism Score

Tourism Score at San Marcos Automatic Weather Observing / Reporting Systembest timebest timeJanFebMarAprMayJunJulAugSepOctNovDec02468106.46.42.52.56.46.45.05.0 precipitationprecipitationcloudscloudstemperaturetemperaturetourism score
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit San Marcos Automatic Weather Observing / Reporting System for hot-weather activities is from late May to mid September, with a peak score in the last week of June.

Beach/Pool Score

Beach/Pool Score at San Marcos Automatic Weather Observing / Reporting Systembest timeJanFebMarAprMayJunJulAugSepOctNovDec02468106.66.60.60.6 precipitationprecipitationcloudscloudstemperaturetemperaturebeach/pool score
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at San Marcos Automatic Weather Observing / Reporting System typically lasts for 9.0 months (272 days), from around February 28 to around November 27, rarely starting before January 29 or after March 26, and rarely ending before November 6 or after December 16.

Time Spent in Various Temperature Bands and the Growing Season

Time Spent in Various Temperature Bands and the Growing Season at San Marcos Automatic Weather Observing / Reporting Systemgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Feb 2850%Feb 2850%Nov 2750%Nov 2790%Mar 2690%Mar 2690%Nov 690%Nov 610%Jan 2910%Jan 2910%Dec 1610%Dec 160%Jan 50%Jan 5Jul 18100%Jul 18100%very coldcoldcoolcomfortablewarmhotsweltering
The percentage of time spent in various temperature bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms at San Marcos Automatic Weather Observing / Reporting System should appear around January 20, only rarely appearing before January 12 or after February 2.

Growing Degree Days

Growing Degree Days at San Marcos Automatic Weather Observing / Reporting SystemJanFebMarAprMayJunJulAugSepOctNovDec0°F1,000°F2,000°F3,000°F4,000°F5,000°F6,000°F7,000°FJan 2090°FJan 2090°FApr 12900°FApr 12900°FMay 231,800°FMay 231,800°FDec 316,764°FDec 316,764°F
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.

The brighter period of the year lasts for 4.1 months, from April 12 to August 17, with an average daily incident shortwave energy per square meter above 6.2 kWh. The brightest day of the year is June 14, with an average of 7.0 kWh.

The darker period of the year lasts for 2.7 months, from November 12 to February 3, with an average daily incident shortwave energy per square meter below 3.9 kWh. The darkest day of the year is December 19, with an average of 3.1 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy at San Marcos Automatic Weather Observing / Reporting SystembrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWh8 kWh9 kWhJun 147.0 kWhJun 147.0 kWhDec 193.1 kWhDec 193.1 kWhApr 126.2 kWhApr 126.2 kWhAug 176.2 kWhAug 176.2 kWhFeb 33.9 kWhFeb 33.9 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Data Sources

This report illustrates the typical weather at San Marcos Automatic Weather Observing / Reporting System, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

San Marcos Automatic Weather Observing / Reporting System has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back include but are not limited to San Marcos Municipal Airport; New Braunfels Municipal Airport; Austin-Bergstrom International Airport; Bergstrom AFB / Austi; Austin City, Austin Camp Mabry; Randolph Air Force Base; Austin Executive Airport; and Largo Vista / Rusty Allen Airport.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.